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Laws of Atomic Theory - how is this possible?

Generally in science, a theory is effectively a fact. The theory of evolution is not a guess, or a hypothesis. It's currently understood to be a fact, backed up by evidence from numerous scientific fields spanning many decades.

String theory on the other hand seems much more contentious, much less settled in the scientific community. Why isn't it called the string hypothesis?

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This is not true that the word "theory" always indicates certain level of approvement; in most cases it just mean "a set of postulates and their fundamental consequences". – mbq♦ Oct 1 '11 at 22:42
The theory of "Evolution by natural selection" is most definitely a guess, it competes with "evolution by sexual selection" and "evolution by random drift", among other ideas. The undeniable fact here is common descent, which says that we came from monkeys and germs by a process of gradual change. This is never called the "theory of common descent". – Ron Maimon Oct 1 '11 at 22:58
I would say that a theory is a model that generates an apparant prediction. – Anders I Oct 2 '11 at 0:08
I would refer you to my comments on Laws of Atomic Theory - how is this possible?. Indeed I consider these questions as fairly equivalent and equally marginal for Physics.SE, though I rather agree with David's point (on the earlier question) that English.SE might flub it. – dmckee♦ Oct 2 '11 at 0:12
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This question is a rightful one! And reason to call string ( and some other) "theories" comes from lack of classic knowledge and more important, You cant get big and lasting grants on hypotheses as a "theorist". :=) – Georg Oct 2 '11 at 11:18
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marked as duplicate by David Zaslavsky♦ Oct 2 '11 at 0:57

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These terms are not used consistently, nor in a way consistent with the way people who talk about science interpret them. For example, the thing called the "standard model" is not really a model anymore (except for the Higgs sector), but an excellent theory, perhaps even a fact of nature, but it is still called the "standard model", not the "standard fact".

An open-ended program you can publish new fundamental papers about is always called a "theory". A "model" is something that was perfectly and precisely well defined in the original paper, like the Weinberg-Salam model. A "law" is a simple mathematical relation that comes either from experiment or theory. A "hypothesis" is a tentative guess, and turns into a theory when you can start writing papers about it. A "principle" is a hypothesis that you really believe in.

These terms are more publishing terms than philosophical terms, and don't give them too much respect.

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